1. Field of the Invention
This application is claiming the benefit, Under 35 U.S.C. xc2xa7119(e), of the provisional application filed on Mar. 20, 1998, under 35 U.S.C. xc2xa7111(b), which was granted Ser. No. 60/078,848, and of the provisional application filed on Apr. 29, 1998, under 35 U.S.C. xc2xa7111(b), which was granted Ser. No. 60/083,484. The provisional applications, Ser. Nos. 60/078,848 and 60/083,484 are hereby incorporated by reference.
The present invention relates to a biological fluid filter for use in filtering biological fluid products into their therapeutically valuable components. The filter media used in the biological fluid filters of the prior art are chosen or modified in order to have a critical wetting surface tension (CWST) in the proximity of the surface tension (ST) of the biological fluid to be filtered. If the CWST of the media is substantially lower than the ST of the biological fluid being filtered, the priming time for the filter increases as the difference between the CWST and the ST increases.
If the CWST of the media is substantially higher than the ST of the fluid, the filter media is easily wetted by the biological fluid. In cases where the filter media is easily wetted by the biological fluid, air may be entrapped within the filter device, which results in reduction of the useable filter area, and the decreased performance.
In the present invention, a filter device is introduced which eliminates or minimizes gas entrapment. The device is not limited by the CWST of the filter media, or the ST of the fluid to be filtered. Also, the device improves the filter priming time. These benefits are achieved by dividing the filter medium into two or more sections, separated from each other, so that the wicking properties of the filter medium used will not cause any substantial air entrapment in the biological fluid filter device.
2. Discussion of the Related Art
Methods and apparatus for processing blood are well known in the prior art. U.S. Pat. No. 3,892,236 to Djerassi shows an apparatus for the continuous withdrawal of blood from a human donor, forced extracorporeal circulation of blood of the donor with separation of granulocytes, and return by gravity of the leukocyte-poor whole blood to the donor.
U.S. Pat. No. 5,126,054 to Matkovich shows a venting means for venting gas from the transfer line of a liquid delivery system comprising a housing, a first, liquid-wettable, microporous membrane carried in said housing so as to be in communication with the transfer line, and a second, non-liquid-wettable, gas permeable microporous membrane superimposed on said microporous membrane to the outward side of the housing. Gas in the delivery system is vented from the system so long as the first microporous membrane remains unwetted by the delivery liquid.
U.S. Pat. No. 5,451,321 to Matkovich shows biological fluid processing assemblies having a gas inlet, and/or a gas outlet.
While these devices are generally satisfactory, some of the methods and apparatus of the prior art leave a large amount of biological fluid trapped in various elements of the fluid processing apparatus. While the aforementioned U.S. Pat. No. 5,451,321 to Matkovich provides for liquid trapped in various elements of the blood processing system to be recovered either by causing a volume of gas behind the entrapped liquid to push the liquid through those elements and into the designated collection bag, or by pulling the entrapped liquid into the designated collection bag by a pressure differential (e.g. gravity head, pressure cuff, suction and the like), the system still has several drawbacks. One drawback is that they require one or more nonwettable, gas permeable, membranes. This requirement can lead to increased costs over wettable membranes.
Therefore, those skilled in the art continue to search for a method and apparatus to provide for optimal recovery of the biological fluid from biological fluid processing systems, cost reduction and ease of use, and have developed novel open and closed loop systems and methods associated therewith to achieve this goal.
The problems of the prior art are solved by the present invention utilizing novel open and closed loop biological fluid processing systems which all share the concept that the gases transferred into, out of, or within the biological fluid processing system have the transfer lines arranged or configured in a manner which precludes the biological fluid from ever contacting the upstream and downstream gas inlet or outlet housings or vents, or bypassing the fluid filtration or leukocyte depletion device. Gases are transferred into and out of the biological fluid processing systems through a porous medium in the upstream and downstream gas inlet housings or vents. Each housing or vent is separated from, and in communication with the biological fluid by a column of gas in the transfer lines. The upstream gas inlet housing or vent is in communication with the unfiltered biological fluid and the downstream inlet or vent is in communication with the filtered biological fluid.
In one embodiment of the present invention, a biological fluid filtration apparatus is provided which includes a fluid filtration or leukocyte depletion device having an inlet and an outlet, a fluid container upstream from and elevated above said fluid filtration or leukocyte depletion device and having an outlet, a first conduit in fluid communication with the outlet of said fluid container and the inlet of said fluid filtration or leukocyte depletion device, a receiving container downstream of said fluid filtration or leukocyte depletion device and having an inlet, a second conduit in fluid communication with the inlet of said receiving container and the outlet of said fluid filtration or leukocyte depletion device, an upstream gas inlet having one of its+ ends elevated above said fluid container, and having its+ other end in fluid communication with said first conduit, and a downstream gas inlet having one of its+ end elevated above said fluid container, and having its+ other end in fluid communication with said or leukocyte depletion or fluid filtration device.
In another embodiment of the present invention, there is provided a closed loop fluid filtration or leukocyte depletion device including a fluid filtration or leukocyte depletion device having an inlet and an outlet, a fluid container upstream from, and elevated above, said fluid filtration or leukocyte depletion device and having an outlet, a first conduit in communication with the outlet of said fluid container and the inlet of said fluid filtration or leukocyte depletion device, a receiving container downstream of said fluid filtration or leukocyte depletion device and having an inlet, a second conduit in fluid communication with the inlet of said receiving container and the outlet of said fluid depletion device and a bypass line in fluid communication with said fluid container and said receiving container and having a loop portion elevated above said fluid container.
In yet another embodiment of the present invention the upstream gas inlet is eliminated and the downstream gas inlet is connected to the receiving container instead of the fluid filtration or leukocyte depletion device.
In another embodiment of the present invention, the downstream gas inlet may be eliminated.
In still another modification of the present invention, the upstream gas inlet housing or vent and the downstream gas inlet housing or vent may be part of the same inlet device.
Thus, it is an object of the present invention to provide an improved method and apparatus for filtering biological fluids.
It is a further object of the present invention to provide an open gas vent that prevents premature gas introduction into the fluid stream in a biological fluid processing system.
It is a further object of the present invention to provide an open loop biological fluid processing system with transfer lines or conduits arranged or configured in a matter which precludes the biological fluid from contacting the upstream and downstream gas inlet housings or vents, or bypassing the biological fluid depletion device.
Another object of the present invention is to offer a wider choice of materials which may be used in the gas inlet housings or gas outlet housings or vents of biological fluid filtration systems. The present invention does not require wettable membranes. The choice of membranes for the present invention is not limited.
Another object of the present invention is to provide a system of the foregoing nature where gas is transferred into and out of the biological fluid processor through porous medium in the upstream and downstream gas vents.
A still further object of the present invention is to provide an open loop system of the foregoing nature where each gas vent is separated from, and in communication with the biological fluid by a column of gas in the transfer lines or conduits.
A still further object of the present invention is to provide an open loop biological fluid filtration system of the foregoing nature wherein the upstream gas inlet housing or vent, and the downstream gas inlet housing or vent may be a portion of the same inlet device.
A still further object of the present invention is to provide a closed loop biological fluid filtration system having a bypass line bypassing the biological fluid filtration device, the bypass line is arranged such that a column of gas separates the unfiltered biological fluid upstream of the filtration device from the filtered biological fluid downstream of the biological fluid filtration device.
A further object of the present invention is to provide an open loop biological fluid filtration system having an upstream gas inlet elevated above the level of the biological fluid container and having a satellite bag connected to the biological receiving fluid container.